Why dieters have fat chance of losing weight

Diets are not a good way to lose weight in the long term, according to researchers. They found that although dieters can lose significant amounts of weight in the first few months, most will return to their starting weight within five years.

"Diets do not lead to sustained weight loss or health benefits for the majority of people," said Traci Mann, a psychologist at the University of California, Los Angeles.

"You can initially lose 5% to 10% of your weight on any number of diets, but then the weight comes back. We found that the majority of people regained all the weight, plus more. Sustained weight loss was found only in a small minority of participants, while complete weight regain was found in the majority."

Prof Mann analysed 31 long-term studies that had followed people for between two and five years on a range of diets. Her results, published in the April issue of the journal American Psychologist, concluded that most would have been better off not dieting. "Their weight would be pretty much the same, and their bodies would not suffer the wear and tear from losing weight and gaining it all back."

Repeatedly losing and gaining weight has been linked in previous studies to cardiovascular disease, stroke, diabetes and altered immune function.

Prof Mann found that although dieters typically lost up to 10% of their starting weight in the first six months, at least one-third to two-thirds of people on diets regain more weight than they lost within four or five years.

Among those who were followed for more than two years, 83% eventually gained back more weight than they lost - one study showed that half of dieters weighed more than 4.99kgs (11lb) more than their starting weight five years after the diet.

Another study examined a variety of lifestyle factors and their relationship to changes in weight in more than 19,000 healthy older men over four years.

According to Janet Tomiyama, a psychologist at UCLA who also worked on the analysis, the study showed that "one of the best predictors of weight gain over the four years was having lost weight on a diet at some point during the years before the study started".

Judy More, spokeswoman for the British Dietetic Association, said that the results of the study were not surprising. "When people are on a diet, people feel as if they're denying themselves things so when they come off it they think, oh thank God I can go back to eating."

She added that people who wanted to lose weight should look at the challenge as a change in lifestyle.

"They have to look at it not as a diet where they're denying themselves because eventually people get sick of that and go back to their previous lifestyle.

"What they've got to think about moving towards is a new lifestyle but doing it through small, sustainable changes. They've got to find a physical activity they enjoy, whether it's walking or going to the gym or taking up a new sport."